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TAMU PSYC 311 - Sex, Mating, Parenting, cont.
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PSYC 311 1st EditionLecture 22Current LectureApril 21- Runaway Selectiono Exaggeration of a trait One “locus” houses alleles that code for male traits that females prefer  Other locus houses alleles that code for female preference - Assume that loci are switched on in males (color) differently from femalepreference o As one increases, so does the othero Epigamic selection and female choice Very high female investment/burden o Slide 48- Questions females must ask o Is he my species  Pre-reproductive isolating mechanisms - Attire, general appearance - Calls (bell birds, very loud)o Tui bird: mimic-vocalization used o Kookaburra – territorial defense via localizations o Does the prospective mate have superb male genetic fitness as indicated by  High rank in dominance hierarchy/possession of superior territory  Superior phenotype indicative of superior genotype Responses of females’ inciting “fight over me” Old age, handicap (injury, one horn)- Indicates high survivability o Does potential mate demonstrate investment value Quality of territory (food, protection, location) Willingness to share Protection of females and offspring Sharing parental obligations Gifts presented to females that may prevent cannibalism (Empid flies)- Females in some species (praying Mantids) eat males  males protein and offspring  Traumatic insertion (ie: stabbing)- Evolution of mating systems o Monogamy – one male for each female  Seasonal vs. serial, social vs. genetic (16% in humans) Males needed after fertilization – adaptive - Male guarding – male may guard a female (especially if female remains receptive after mating or female disperses)- Mate assistance – parental careo If male is available immediately after birth, he is likely to mate with her again o Male seahorse, male 3-spined stickleback - Female enforced monogamy o Females attack mates if show signs of philandering o Females prevent males from sexually attractive displays  Rare in mammals – see slides o Polygamy – more than 1 male/female for each male/female Polygyny – more than one female per male (84% of humans)- Female defense polygyny o Males compete to sequester a group of females  Female distribution theory – females flock/herd groups together for foraging and protection  Allows males to control group o Resource defense polygyny  Territorial quality  See slides - Why polygyny?o Polygyny threshold model: quantity/quality of resources controlled by males varies greatly o “scramble competition polygyny” – males race to locate and mate with as many females as possible o Explosive breeding assemblage – females clustered during brief breeding season - Lek – courtship display area o Males compete in lek area, females come to watch o Leks are surrounded by no resources  Displays can attract predatorso Why do females tend to mate with same males at lek?o Lek paradox o See slides  Polyandry – more than one male per female (rare, less than 1%)- Genetic benefitso Fertility insurance hypothesiso Good genes hypothesiso Genetically compatibility hypothesis - Material benefits o More resources hypothesiso Better protection hypothesiso Infanticide reduction hypothesis - Sex role reversal o Females compete with one another for males/territory o Males provide all parental care - Polygyandry – several males share several females - Promiscuity – multiple partners, little time spent with eacho Extra pair copulations  Males and females both ensure genetically diverse offspring  Benefits males and females See slides - Evolution of parental behavior o Orian – whatever increases proabilty of some offspring surviving to reproduce at cost of paren’ts ability to generate additional new offspring (C/B)  Pre-zygotic vs. post-zygotic - See slides o Why is parental behavior more maternal than paternal? Milk from mothers in mammals  Exceptions - Male emperor penguin – cradles egg on top of ice - Male mallee fowl o C/B of being a parent for males  See slides 95-96o Interspecies brood parasitism  Eggs of a brook parasitic species are placed into nest of host species - Host species has cost of raising another species’ offspring - Good for BPS, not for HSo Mimicry of host bird eggs and gape of its hatchlings is important Cowbird and warbler eggs - Size of egg  How did cuckoos/cowbirds evolve to parasitize the broods of other birds?- Gradual scenario – parasitizing species initially parasitized other of their own species - Parasitizational exploitation from start o Only see results of evolutionary process  IBP can’t be accounted for here  Phenomena associated with BP- Many PS choose smaller species - All birds have larger egg/hatchling preference - See slides- See


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TAMU PSYC 311 - Sex, Mating, Parenting, cont.

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